The census is available on microfilm through any LDS center. The 1841 tends to be of very poor quality - can't remember what the Jurby section is like.
Alternatively, you can get an A3 print of individual pages from the National Archives in the UK.

Change of occupation is very common.

I'm not an expert on the school system, but gvien the population, location, etc. of Jurby, I suspect the school was very lucky to have two teachers. I think "headmaster" is more a courtsey title bestowed by the family.

There was a scheme to certify teachers, male and female. Young people were employed as apprentice teachers. Their occupation in a census is recorded as "pupil teacher". On completion, they were issued a certificate and were known as certified or certificated teachers.